<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>

<script type="text/javascript">
	
	var a = '1';
	a.b = 10;
	alert(a);//'1'
	alert(a.b);//undefined


</script>

</body>
</html>